1. Field of the Invention
The present invention relates to the field of avian egg fertilization. In particular, the present invention relates to a method of fertilizing an egg in a shell.
2. Background Art
Typically, breeding in the poultry industry is carried out by either one of two systems:
Floor Breeding Program
The first system is called xe2x80x9cfloor breedingxe2x80x9d and it is utilized to produce the vast majority of all commercial hatching eggs. In this system males are simply added into the flocks of females at a typical ratio of between 10 and 15 percent. The floor breeding system, even with its inefficiencies, is currently the low-cost system for producing hatching eggs because it requires less labor than competing systems. Average hatch rates range from approximately 83% for broiler breeders to 92% for layer breeders. Even though this system has been the backbone of the poultry industry for many years, it has many limitations.
Size Versus Reproductive Capacity
Floor breeding is no longer practiced at all in turkeys due to the intense selection for increased muscle yield that has rendered commercial turkey breeds incapable of natural mating. The same trend is being seen in broilers. Selection for increased size in broilers has compromised fertility and mating ability and it is predicted that fertility will continue to decline as body weights increase. This presents a dilemma for poultry producers because decreases in fertility have a direct negative impact on their bottom line.
Inefficient Waste Removal
Natural mating must be performed on solid floors to avoid injury to the birds. This design requirement precludes the use of automated waste removal systems and necessitates manual cleaning between successive flocks of birds. This adds to labor and overhead costs while decreasing the productive use of facilities.
Egg Production and Quality
Since eggs remain in the houses with the flock until collection time; eggs are frequently contaminated with dirt and fecal material which can reduce hatch rates. In addition, typically between 3 and 5% of the eggs produced in floor houses are laid directly on the floor rather than in the provided laying boxes and must be discarded.
Inefficient Space and Equipment Utilization
Maintaining males and females together in a floor house requires the installation of two independent feed and watering systems because of different nutritional and production requirements for each sex. It also requires the installation of laying boxes and automated egg collection systems. All of this equipment occupies limited floor space in the house. For these reasons floor rearing is not an efficient use of housing space and equipment when compared to stacked cage systems.
Mortality and Fertility
Aggressive males tend to fight, leading to higher male mortality rates. Male mortality rates average 13% in floor houses versus 2% in cage houses. Male aggressiveness towards hens during mating gradually takes a toll in the form of increased female mortality, decreased fertility, and a decrease in the length of the egg production cycle. As the males in one flock get older, fertility starts to decline. The standard solution is to xe2x80x9cspikexe2x80x9d the flock with young males to improve fertility. However, this sets off another round of aggression with a short-term decrease in fertility and an increase in mortality. Disease is more common in floor houses because of the constant contact of the birds with bedding and waste material that harbor pathogenic organisms.
Decreased Feed Conversion
Controlling feed costs is critical to running a competitive poultry operation. Feed costs can account for up to 60% of the cost of raising a broiler chick, for instance. In one study, birds raised on the floor consumed 20% more food for the same amount of production when compared to those raised in cages. This difference is due to the increased level of social interactions as well as the generally higher level of physical activity seen in floor houses. Males consume more feed than females, making the floor breeding system inefficient with respect to feed consumption due to the large numbers of males that must be maintained.
Limited Flexibility in Breeding Strategies
Due to the fact that males and females are housed in one large group in the floor breeding house arrangement, the breeder is very restricted in their ability to perform advanced crosses and selections on the breeding stock. For this reason floor houses are primarily utilized as a tool for the multiplication of pre-selected genetic stocks to produce final commercial crosses.
Artificial Insemination Breeding Program
Another system utilized to generate hatching eggs is called artificial insemination (AI). AI is widely practiced by xe2x80x9cprimary breedersxe2x80x9d at the top of the breeding pyramid but not generally used by commercial producers at the bottom of the pyramid. Primary breeders are companies that own and improve the elite pedigreed genetic lines that are crossed to produce the final commercial products-broilers, layers and turkeys. The quantities of birds increase exponentially as you move down the breeding pyramid from the pedigreed lines through the grandparent stock, parent stock, and finally to the actual commercial birds. While birds of elite genetic makeup at the top of the pyramid are very expensive, birds at the bottom are inexpensive. For these reasons, different operational models are utilized for reproduction at different level.
In the AI system, males and females are housed in the same houses but are caged separately. The female cages typically hold between two and five hens, while the male cages hold a single rooster. AI programs address many of the limitations of the floor breeding houses listed above. For example, since cage houses are utilized, waste removal can be performed automatically. Houses are generally much cleaner, leading to fewer disease problems. Egg production is improved because eggs roll out of the cages and is not laid on dirty floors. Equipment and housing space are utilized more efficiently. Mortality is minimized due to a decrease in social aggression and disease. Fertility levels are maintained more consistently because social and physical interaction are eliminated from the process of reproduction. Feed conversion is increased. And finally, the production system has increased flexibility for doing advanced crosses and selections. This capability is absolutely required by primary breeders in order to improve their genetic stocks and to stay competitive in the marketplace. While most of the advantages listed above are also important for commercial-level multiplication breeders, they are offset by one crucial shortcoming, the high labor costs associated with AI programs.
AI programs replace the innate sexual drive of poultry with human labor. Workers must manually collect semen from males in cages and inseminate females in cages on a 7-day rotation. The level of sophistication required in these programs mandates a skilled workforce. For this reason, the AI program, though operationally superior, is economically impractical for commercial-level breeding programs. Even the use of dwarf hens, an innovation that allows similar egg production with about 30% less feed consumption, can not justify the increased labor costs of the Al program for commercial level multiplication breeders.
At the time of ovulation, the avian oocyte comprises a blastodisc, or germinal disc, which contains the female pronucleus, and a yellow yolk mass. The germinal disc and yolk mass are surrounded by the oocyte cell membrane, called the oolemma. Surrounding the oolemma is the perivitelline layer (PL), also referred to as the inner perivitelline layer (IPL). The space between the oolemma and the IPL is termed the perivitelline space, which is traversed by granulosa cells. Once the oocyte is released from its ovarian follicle, it is referred to as an ovum. The ovum moves into the oviduct where it is engulfed by the infundibulum, where fertilization occurs if sperm are present.
As the ovum passes into the posterior infundibulum, another layer, the outer perivitelline layer (OPL), surrounds the ovum. This membrane acts to prevent polyspermy, which is a lethal condition that occurs when multiple sperm bind to and penetrate the ovum at the region of the blastodisc (Koyanagi et al., xe2x80x9cFate of spermatozoa that do not participate in fertilization,xe2x80x9d Cell Tissue Res., 1981; 214 (1): 89-95; Okamura et al., xe2x80x9cThe passage of spermatozoa through the vitelline membrane in the domestic fowl Gallus gallus,xe2x80x9d Cell Tissue Res., 1978; 188(3): 497-508; Bakst et al., xe2x80x9cHydrolysis of the Hen""s Perivitelline Layer by Cock Sperm in vitro,xe2x80x9d Biol. Reprod., 17: 370-379). The egg is then surrounded with additional layers of chalaza and thick and thin layers of albumen. When the ovum moves into the isthmus, two shell membranes are deposited, upon which small crystals of calcium carbonate are deposited, thus beginning the formation of the shell.
The preceding events all occur within the first few hours following fertilization. The ovum next moves into the uterus, where over the next 18-20 hours, the calcium shell is completed. The egg then moves into the vagina for several minutes, and then is extruded from the vagina, or oviposited (i.e., xe2x80x9claidxe2x80x9d). At this point, if the egg has been fertilized, the embryo contained therein will have 40,000 to 70,000 cells. (Johnston (xe2x80x9cIn Vitro Sperm Binding, Penetration, and Fertilization of Recently Oviposited Chicken Eggs,xe2x80x9d December 1988, Clemson University); Olsen, M. W., J. Morph. 70: 413-533 (1942); Etches et al., in Methods in Molecular Biology, vol. 62 Recombinant Gene Expression Protocols, Ed. R. Tuan, Humana Press, Inc. Totowa, N.J., pp. 433-450 (1997); Petitte et al., in Manipulation of the Avian Genome, Ed. Etches et al., CRC Press, Boca Raton, Fla., pp. 81-101 (1993)).
The present invention provides a ground-breaking improvement in avian biology by making it possible to fertilize an oviposited egg in its shell, to obtain embryo development, and to hatch a live bird from the shell, herein called xe2x80x9cin ovo fertilization,xe2x80x9d (IOF). Such methods provide an alternative to floor breeding and IV fertilization that can greatly increase the efficiency of poultry production.
The present invention relates to the field of avian egg fertilization. In particular, the present invention provides a method of fertilizing an egg in a shell. The invention also provides a method of fertilizing an egg in a shell, whereby a live chick is hatched. The invention also provides developmentally early stage oviposited avian eggs.
As used herein, xe2x80x9ca,xe2x80x9d xe2x80x9canxe2x80x9d or xe2x80x9cthexe2x80x9d may mean one or more. For example, xe2x80x9canxe2x80x9d egg may mean one egg or more than one egg. Moreover, xe2x80x9cthexe2x80x9d egg may mean one egg or more than one egg.
The present invention provides a method of fertilizing an avian egg in a shell, wherein the egg comprises a yolk enclosed by a membrane, comprising obtaining a sperm sample comprising avian sperm in a physiologically acceptable carrier, and delivering the sperm sample into the egg, so as to fertilize the egg. The present invention relates to the unexpected and surprising discovery that an unfertilized, oviposited avian egg can be fertilized in the shell and produce a live chick. As used herein, reference to an avian egg in a shell refers to an oviposited egg, that is, an egg with a calcium carbonate shell that has been extruded from the vagina of the bird. Extrusion of the egg is referred to as xe2x80x9coviposition.xe2x80x9d Accordingly, all references herein to an xe2x80x9cegg in a shellxe2x80x9d or to an xe2x80x9coviposited eggxe2x80x9d should be understood to be equivalent in meaning. The process of fertilizing an oviposited egg in a shell is referred to herein as xe2x80x9cin ovo fertilizationxe2x80x9d (IOF).
An avian egg comprises a hard, calcified shell at the time the egg is oviposited. Within the shell is a yolk that contains nutrients for supporting growth and development of an embryo. As used herein, an xe2x80x9cembryoxe2x80x9d is a developing organism resulting from the joining of a female pronucleus and a male pronucleus during the process of egg fertilization. While a fertilized (single cell) ovum may thus be called an embryo, the single cell embryo is also specifically referred to herein as a zygote.
Although in ovo fertilization can be performed on eggs as old as 2 weeks if the eggs are maintained at room temperature, ideally newly oviposited eggs are used for the best results. In a preferred embodiment, the sperm sample is delivered into the egg between 0 and 96 hours following oviposition. In a more preferred embodiment, the sperm sample is delivered into the egg between 0 and 72 hours following oviposition. In an even more preferred embodiment, the sperm sample is delivered into the egg between 0 and 48 hours following oviposition. In a highly preferred embodiment, the sperm sample is delivered into the egg between 0 and 24 hours following oviposition. Thus, it is preferred that the sperm sample be delivered into the egg as soon as possible following oviposition. However, the precise timing of fertilization can depend on how the oviposited egg is maintained, e.g., temperature, humidity, etc. For example, fertilization can improve if the unfertilized oviposited egg is fertilized before it is allowed to cool.
The sperm in the sperm sample may be obtained from a bird by methods known to a person skilled in the art, such as the abdominal massage method which is well-known to those of skill in the art. This method allows the collection of an ejaculate (semen) comprising sperm, seminal fluid, and transparent fluid. Transparent fluid is a lymphlike fluid that passes from the lymph channels to the surface of the phallus during phallic tumescence. Avian sperm may also be obtained from commercial sources that are well known to those of skill in the art.
In one embodiment, the sperm in the sperm sample is from a single bird. In another embodiment, the sperm in the sperm sample is a mixture of sperm obtained from more than one bird. When a mixture of sperm from more than one bird is used in the methods of the invention, the probability of successfully fertilizing the egg can increase, because if one of the birds from which the sperm has been collected is infertile, it is possible that the sperm collected from the other bird or birds will be capable of fertilizing the egg.
In a preferred embodiment, the sperm sample comprises sperm from birds which are members of the same species, and the sperm sample is used to fertilize eggs oviposited by hens which are members of the same species as the sperm donors. The present invention also contemplates the use of sperm from one species and an egg from another species, if the sperm is capable of fertilizing the egg.
While it is typically preferred that the sperm be used within 30 minutes of the time that it is collected, older sperm, and even sperm which have previously been frozen or freeze dried may be used in the methods of the invention, as long as the sperm retain their ability to fertilize an ovum. Where the sperm are to be used more than 30 minutes after collection, it is preferred that they be combined with a sperm extender, as is described below.
As mentioned above, the sperm sample also comprises a physiologically acceptable carrier. As used herein, a xe2x80x9cphysiologically acceptable carrierxe2x80x9d is a fluid in which sperm remain motile and viable. Examples of a physiologically acceptable carrier include, but are not limited to, unaltered semen, seminal fluid (either original to the sperm or added), transparent fluid (either original to the sperm or added), buffered saline solution, sperm extender, and combinations thereof. Preferably, the carrier includes sperm extender, also referred to in the art as a diluent. As mentioned above, the use of a sperm extender is especially preferred where the collected sperm will not be used for fertilization within 30 minutes after collection. M. R. Bakst, In Manipulation of the Avian Genome, R. J. Etches and AM. Verrinder Gibbons, eds., CRC Press, Boca Raton, Fla., pp. 15-28 (1993). As used herein, a xe2x80x9csperm extenderxe2x80x9d is a physiologically acceptable carrier that is used to dilute a sperm sample to produce a sperm sample of greater volume in which the sperm are less concentrated. Preferably, the composition of the sperm extender will extend the shelf life of the sperm, as well as diluting the sperm so as to increase the number of eggs which may be fertilized by the quantity of sperm which has been collected. Examples of sperm extender compositions, suggested dilution rates, optimal storage times and conditions, and commercial sources of extender may be found in Bakst (xe2x80x9cPreservation of Avian Cells: In: Poultry breeding and Genetics, R. D. Crawford (ed.) Elsevier, N.Y., pp 91-108 (1990)). Other diluents commonly used in the poultry industry are Lago Formulation Avian Semen Extender by Hygeia Biological Laboratories, Semaid Turkey Extender by Poultry Health Laboratories in Davis Calif., Beltsville Poultry Semen Extender by Tri Bio Laboratories, Inc. in State College, Pa. In a preferred embodiment, the sperm extender is Avidiluent. Avidiluent is produced by IMB, 10 rue Georges, Clemenceau, BP 81, 61302 1"" Aigle, France.
Thus, in one embodiment, the sperm sample may comprise sperm and seminal fluid, i.e., semen. Moreover, the sperm sample may comprise sperm and seminal fluid which is diluted with a physiologically acceptable carrier, including but not limited to buffered saline solution and a sperm extender.
The sperm sample can also be prepared by methods which will be clear to one of ordinary skill in the art, such as washing semen from one or more birds with a solution such as buffered saline solution or sperm extender, centrifuging the resulting solution, removing the supernatant, and resuspending the washed sperm in a volume of a solution such as buffered saline or semen extender. One of ordinary skill in the art will readily understand how to achieve the desired concentration of sperm by resuspending the sperm in the appropriate volume of solution. For example, following centrifugation and removal of supernatant, the packed sperm may then be weighed, and the number of sperm then estimated by using known values for the weight of avian sperm. The sperm may then be resuspended in the volume required to obtain the desired sperm concentration. Alternatively, the centrifuiged sperm may be resuspended following removal of the supernatant, and then recentrifuiged, allowing the determination of the packed sperm volume. (Johnston S., xe2x80x9cIn Vitro Sperm Binding, Penetration, and Fertilization of Recently Oviposited Chicken Eggs,xe2x80x9d M. S. Thesis presented to the Graduate School of Clemson University, 1998). Subsequently, the concentration of the sperm may be calculated using the formula of Maeza and Buss. (Poultry Sci. 55:2059 (1976)).
Typically, the concentration of sperm in chicken semen is from 300 million to 800 million per milliliter, in turkey semen from 800 million to 1.5 billion per milliliter, in Guinea fowl semen from 400 million to 800 million per milliliter, in Pekin duck semen from 20 million to 600 million per milliliter. The standard number of sperm used for artificial insemination is 100 million in a total volume of 50 micro liters. In the methods of the present invention, because sperm are placed directly adjacent to the female pronucleus, far fewer sperm are required to fertilize the egg. Thus, as few as one sperm can be used in the methods of the present invention. In fact, a large range of sperm concentrations can be used in the present invention. In one embodiment, chicken semen is diluted with an equal volume of Avidiluent and approximately 0.01 milliliters of this sperm sample is injected into an egg. Thus, approximately 1 million sperm would be deposited adjacent to the female pronucleus.
In the methods of the invention, fertilization of the avian egg in the shell is accomplished by delivering the sperm sample into the egg. Delivery of the sperm sample may be accomplished by any method which will allow the sperm to be delivered inside the shell, including, but not limited to, dissolving an area of the shell with, e.g., an acid solution, using electroporation, and creating an opening by penetrating or cracking an area of the shell, for example using a tool such as a needle or a scalpel.
Preferably, the surface of the area of the shell to be penetrated in order to deliver the sperm sample is sanitized before the sperm is delivered inside, to prevent contamination of the egg. Any method which is compatible with the delivery method may be used to sanitize the shell, including, but not limited to, the disinfectant IOFEC-20(copyright), and 3% hydrogen peroxide. The surface of the egg at the intended penetration site may be wiped or sprayed with the disinfectant, or the egg may be immersed in a vessel containing the disinfectant of choice.
As is described above, an opening in the shell can be made with a tool such as a knife or a needle. Preferably, the tool will be sterile. For example, in a two-step procedure, an opening in the shell can first be made with a knife or other sharp instrument. In a second step, a needle attached to a syringe containing a sperm sample can be passed through the opening to deliver the sperm sample into the egg. Introduction of the sperm sample into the opening in the shell may also be accomplished by other means, including, but not limited to, the use of a pipette, such as a micropipettor. Alternatively, in one step, a needle attached to a syringe containing the sperm sample can be used to penetrate and thus create the opening in the shell and deliver by injection the sperm sample into the egg. Thus, xe2x80x9copeningxe2x80x9d can include a hole created by a needle. Of course, one of ordinary skill in the art will be able to choose a needle whose gauge will be large enough to allow the sperm sample to be moved through the needle. In one embodiment, the needle will be of the smallest gauge that can deliver intact sperm into the shell and also be sturdy enough to penetrate the calcium eggshell. Alternatively, a separate needle or other device could be used to make the opening in the eggshell. Typically, needles varying from 30-gauge to 16-gauge can be used. In one embodiment a 22-gauge needle is used. A sperm is approximately 0.5 um at its widest point and 100 um in length. Therefore, in a preferred embodiment, a needle with an inner diameter of at least 10 um can be used for injections. In one embodiment the needle can remain in the shell after injection. Various needles and methods now used for injection of vaccines into eggs could be used or adapted for delivery of sperm.
The egg injection mechanism may be of a design similar to those manufactured and sold by Embrex, Inc., Merck Inc., and others in the industry. As an example, one design is disclosed in U.S. Pat. No. 4,903,635, entitled xe2x80x9cHigh Speed Automation Injection System for Avian Embryos,xe2x80x9d which is incorporated herein by reference. As described in the patent, the disclosed device is a high-speed automated injection system for avian embryos, which can inject eggs with fluid substances, specifically an inoculating fluid. The machine includes suction devices which lift eggs out of engagement with surfaces, rather than pushing them, before injecting them. Thus, the machine provides separate mechanisms and devices for first forming an opening in the egg shell and then injecting the avian embryo or the surrounding environment with a fluid substance, avoiding use of a single needle or punch to both puncture the shell of an egg and deliver fluid substances to the interior of the egg. As is also known in the art, the present invention here also contemplates using a single needle both to puncture the shell and to deliver fluid substances. Other relevant patents that disclose injection of fluids into eggs include U.S. Pat. No. 5,900,929, entitled xe2x80x9cMethod and Apparatus for Selectively Injecting Poultry Eggsxe2x80x9d; U.S. Pat. No. 5,722,342, entitled xe2x80x9cOvo Antibiotic and Microbial Treatment to Diminish Salmonellae Populations in Aviansxe2x80x9d; U.S. Pat. No. 5,699,751, entitled xe2x80x9cMethod and Apparatus for in Ovo Injectionxe2x80x9d; U.S. Pat. No. 5,438,954, entitled xe2x80x9cMethod and Apparatus for Early Embryonic in Ovo Injectionxe2x80x9d; U.S. Pat. No. 5,339,766, xe2x80x9cMethod of Introducing Material into Eggs During Early Embryonic Developmentxe2x80x9d; U.S. Pat. No. 5,176,101, xe2x80x9cModular Injection System for Avian Embryosxe2x80x9d; U.S. Pat. No. 5,158,038, xe2x80x9cEgg Injection Method, Apparatus and Carrier Solution for Improving Hatchability and Diseasexe2x80x9d; and U.S. Pat. No. 5,136,979, xe2x80x9cModular injection system for avian embryos,xe2x80x9d all of which are incorporated by reference. In the simplest embodiment for IOF, sperm is substituted for antigen in these machines and the depth of injection is adjusted to accomplish IOF.
The opening can be made anywhere in the shell that effects viable fertilization, but is typically made in an area of the shell that is near the germinal disc. While an egg may be manipulated so as to place the germinal disc at different regions of the egg, the germinal disc in a newly oviposited egg is located at the large end of the shell, which overlies the air cell adjacent to the yolk. Once an opening has been created in the shell, the sperm sample is preferably delivered by introducing the needle, pipette, etc., through the air cell and beneath a membrane lying below the air cell (inner shell membrane). The sperm number can be increased or decreased, depending on where and in what form the sperm are administered. In a further preferred embodiment, the sperm sample is delivered into the egg using a needle. In nature, the sperm cells must penetrate the inner perivitelline membrane and fuse with the oolema for successful fertilization to occur. With IOF, the sperm cells must also penetrate the outer perivitelline membrane before successful fertilization can occur. To increase the fertilization efficiency, one can treat the OPL. Any treatment which rendered the OPL or yolk membrane more permeable to sperm could be utilized, for example, a non-toxic acid, a proteolytic enzyme or physical abrasion.
In one embodiment, the needle, pipette, etc., is advanced through the shell at an angle of approximately 15xc2x0, penetrating the membrane lining the shell. In a method of the invention, the needle, pipette, etc., can be advanced through the air cell, until it meets the inner shell membrane. A person practicing the method of the invention will know that the tip of the needle, pipette, etc., has encountered the membrane when slight resistance to further advancement of the tip is felt. As the tip is gently advanced, the resistance from the membrane gives way and the tip is allowed to barely penetrate the membrane. The sperm sample can then be delivered into the egg, adjacent to a region of the membrane and that is adjacent to the germinal disc. Therefore, the sperm can be delivered just under the membrane, a process known as intracytoplasmic sperm injection (ICSI). Typical volumes of the sperm sample are as small as 0.005 ml or as large as 0.10 ml. A typical volume of injected sperm sample is about 0.01 ml.
Preferably, to prevent contamination of the egg and death of an embryo, the opening in the shell is sealed. A non-toxic adhesive can be applied directly to the opening in the shell to seal it. Alternatively, a piece of eggshell can be used as a patch to close the opening and may be attached to the shell with a non-toxic adhesive. In one embodiment, the non-toxic adhesive is Elmer""s(copyright) glue. In another embodiment, the adhesive is silicone sealant. Moreover, any xe2x80x9ctissue gluexe2x80x9d can also be used to seal the shell. A xe2x80x9ctissue gluexe2x80x9d is a sterile, non-toxic adhesive used during surgical, operative procedures to bind tissues together.
The method of the present invention can be used to fertilize oviposited eggs from avian species selected from the group consisting of chicken, quail, duck, turkey, pheasant, ostrich, emu, goose, peafowl, grouse, rhea, parrot, cockatiel, cockatoo, parakeets, and other commercially valuable birds.
The present invention also provides a method of fertilizing an avian egg in a shell, wherein the egg comprises a yolk enclosed by a membrane, and hatching a live chick, comprising obtaining a sperm sample comprising avian sperm in a physiologically acceptable carrier, delivering the sperm sample into the egg, so as to fertilize the egg, incubating the egg, and hatching the live chick from the egg. As used herein, xe2x80x9cobtainingxe2x80x9d includes utilizing pre-made and pre-delivered sperm samples.
After the sperm sample has been delivered into the egg according to the methods of the present invention as described above, the egg is incubated until the live chick is hatched. One of ordinary skill will be aware of the amount of time and the preferred conditions for incubating a fertilized egg belonging to a particular species. The following are incubation periods for various species of birds: Chicken-21 days, Quail-23 days, Corunix quail-17 to 18 days, Pheasant-23 days, Turkey-28 days, Duck-28 to 33 days, Goose-28 to 30 days, Parakeet-18 days, Parrots-28 days, Dove-14 days, Mynah-14 days, Finch-14 days, Button Quail-16 days, Valley Quail-21 to 22 days, Swan-30 to 37 days. Incubation of eggs fertilized by the methods of the present invention as compared to naturally fertilized eggs may differ only in that the length of incubation time may be lengthened to include the amount of time that the fertilized egg would have spent within the body of the female prior to oviposition. In a preferred embodiment, the incubation period lasts from 21 to 23 days for chicken eggs. While one of ordinary skill in the art will readily be able to determine the optimal temperature for incubation of an egg from a particular species of bird, typically the incubation temperature is between 95xc2x0 F. and 100xc2x0 F. A chicken egg will be incubated at about 99.5xc2x0 F. In a more preferred embodiment, the temperature at which the chicken egg is incubated will be lowered as the egg nears the point of hatching. Thus, in a currently preferred embodiment, a chicken egg is incubated at 99.5xc2x0 F. from day 1 of incubation to about day 18 of incubation, and at 98.50xc2x0 F. from day 19 of incubation to hatching.
As is well known in the art, the humidity level at which an egg is incubated can be important for bringing the egg to hatch. Thus, typically the egg is incubated at between 75% and 90% humidity. Preferably, the egg is incubated at about 80% humidity. More preferably, the humidity level at which the egg is incubated will be raised as the egg nears the point of hatching. Thus, in a preferred embodiment, a chicken egg is incubated at 80% humidity from day 1 of incubation to about day 18 of incubation, and at 85% humidity from day 19 of incubation to hatching. In a specific preferred embodiment, an egg is incubated at 99.5xc2x0 F. and 80% humidity from day 1 of incubation to about day 18 of incubation, and at 98.50xc2x0 F. and 85% humidity from day 19 of incubation to hatching. As is well known in the art, turning the eggs during incubation is useful for promoting growth of the embryo.
It is further preferred that the incubation of the eggs take place in a commercial incubator. Commercial hatchers and setters are produced by many companies including PAS Reform, Jamesway, Chickmaster, Buckeye, Cumberland, Petersime, Humidaire Incubator Co., etc. Preferably, the eggs are moved from a setter incubator to a hatcher incubator at about 3 days prior to hatch. The hatcher basket allows the egg to lie on its side where the chick can more easily pip out. This basket also allows the chick to walk about immediately after hatch, which is necessary for the chicks development and viability.
In another embodiment, the present invention provides an oviposited avian egg comprising a native embryo having fewer than 40,000 cells, wherein the embryo can develop into a live chick. xe2x80x9cNativexe2x80x9d means growing, living or produced in its place of origin. Thus, a native embryo is an embryo that develops and hatches the same shell in which the female pronucleus was formed. Thus, the embyro is descended from the native ovum. By the time an ovum which has been fertilized naturally has been oviposited, the developing embryo typically has between 40,000 and 70,000 cells. However, the egg of the present invention is fertilized after it has been oviposited in its shell; thus, an embryo developing in the egg of the present invention will at some time during incubation have fewer than 40,000 cells. In fact, at the moment of fertilization, the embryo in the egg of the present invention will have one cell and is a zygote. As the embryo grows within the egg, normal cell division will occur and the number of cells will increase. Thus, the fertilized, oviposited egg of the present invention will at some time during incubation comprise an embryo having, for example, 10,000, 20,000 or 30,000 cells, including less than and between these numbers of cells. Thus, the invention provides an oviposited avian egg comprising an embryo and a native yolk having fewer than 40,000, 30,000, 20,000, 10,000, 5,000, 1,000 or 100 cells, including numbers in between 1 and 40,000. Two commercially preferred avian eggs are chicken and turkey. The chicks which hatch from these eggs can have a normal karyotype and normal development.
In another embodiment, the present invention provides an avian egg in a shell comprising an embryo having fewer than 40,000 cells (e.g. 30,000; 20,000; 10,000; 1,000; 100 and 1 (zygote)), wherein the embryo can develop into a live chick, and wherein the shell has an opening of less than 4 centimeters. In another embodiment, the opening in the shell is less than 2 centimeters. In another embodiment, the opening in the shell is less than 1 centimeter or 0.5 centimeter. In one embodiment, the opening in the shell is only large enough to accommodate a 22-gauge needle. Thus, the opening can be any size between the smallest opening that will permit injection of sperm, up to smaller than the hole required to place an In Vitro fertilized (i.e., outside the shell) ovum back into the shell. By xe2x80x9copeningxe2x80x9d is meant a hole has been made in the egg at some point after oviposition. xe2x80x9cOpeningxe2x80x9d includes an egg where the hole has subsequently been sealed. For example, an egg having a hole created by a needle used to inject sperm and then sealed is, even after sealing, within the definition of avian egg having an opening. The embryo can be either native or non-native to the egg. xe2x80x9cNon-nativexe2x80x9d includes embryos developed from an ovum not native to the shell in which it was oviposited. Two commercially preferred eggs are chicken and turkey.
An egg of the present invention may, for example, be derived from avian species selected from the group consisting of chicken, quail, duck, turkey, pheasant, ostrich, emu, goose, peafowl, grouse, rhea, parrot, cockatiel, cockatoo, parakeets, swan, dove, and other commercially valuable birds. In a commercially preferred embodiment, the egg is derived from avian species used in the methods of the present invention and is selected from the group consisting of chicken, turkey, goose, duck, quail, and pheasant. In a more preferred commercial embodiment, the egg is derived from a chicken. The method can also be effectively utilized on avian species in zoos, e.g., to help preserve endangered species.
The methods of the present invention can also be used for in ovo fertilization of reptilian eggs. Reptilian eggs, similar to avian eggs, comprise a yolk and female pronucleus and are protected by a shell when they are laid. An unfertilized, oviposited reptilian egg can be fertilized in the shell according to the methods of the present invention. In particular, a sperm sample, comprising sperm from one or more reptiles of the same species, is delivered into the unfertilized, oviposited egg through an opening created in the shell and onto the yolk adjacent to the female pronucleus where fertilization occurs.
The in ovo fertilization methods described herein can also be utilized in conjunction with other in ovo procedures. For example, the embryo can be vaccinated after fertilization. Such vaccination procedures are well known to those skilled in the art. Alternatively, such vaccination could occur simultaneous with in ovo fertilization providing however that the vaccine did not prevent development of the embryo.
Additionally, in ovo fertilization can be automated such that multiple eggs are simultaneously fertilized by, for example, injection techniques. Thus, 50, 100, 200, 300 or more eggs could be simultaneously injected.
It will be clear to those of ordinary skill in the art that the methods of the present invention may easily be applied to a large-scale industrial operation, using automation to fertilize newly laid eggs. Accordingly, apparatus which has previously been used, for example, to immunize embryos in eggs can be adapted to instead introduce a sperm sample. Any of these apparatus or other apparatus adapted for sperm injection is within the scope of applicants"" invention
The following Examples are set forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the methods claimed herein can be performed, and is intended to be purely exemplary of the invention and is not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in xc2x0 F. and pressure is at or near atmospheric.